Fluoroalkyl gem-diols



United States Patent Oifice 3,549,698 Patented Dec. 22, 1970 3,549,698FLUOROALKYL GEM-DIOLS Ralph I. Coon, St. Paul, Minn., assignor toMinnesota Mining and Manufacturing Company, St. Paul, Minn., acorporation of Delaware No Drawing. Continuation-impart of applicationSer. No. 449,269, Apr. 19, 1965, and a division of application Ser. No.679,160, Oct. 30, 1967. This application Dec. 13, 1968, Ser. No. 783,753

Int. Cl. C07c 59/10 US. Cl. 260-535 3 Claims ABSTRACT OF THE DISCLOSUREFluoroalkyl gem-diols and their derivatives in which the alkyl group has3 to 20 carbon atoms are formed by treating a 1,2-epoxy perfluoroalkanewith water to produce alpha-alpha-dihydroxy perfluoroalkane carboxylicacids, which are then converted to amides, esters, and numerous othercarbonyl-derived derivatives. The compounds have useful properties basedupon the combination of the gem-diol group and their fluorine content,e.g. as surfactants.

CROSS-REFERENCE TO RELATED APPLICATIONS This application is acontinuation-in-part and division respectively of prior copendingapplications Ser. No. 449,269, filed Apr. 19, 1965, now abandoned, andSer. No. 679,160, filed Oct. 30, 1967, now abandoned.

BACKGROUND OF THE INVENTION This application relates to fluorinatedcompounds and more particularly to certain fiuoroalkyl gem-diolsincluding alpha-alpha-dihydroxy fiuoroalkane carboxylic acids and theircarbonyl-derived derivatives.

Perfluoropyruvic acid and certain of its derivatives are described inUS. Pat. 3,321,517, and hydroxy acids are disclosed in US. Pat.3,202,706 and gem-diols in US. Pat. 3,227,674. However, so far as isknown, the fiuoroalkyl gem-diols and their derivatives as claimed hereinhave not been known heretofore.

SUMMARY OF THE INVENTION The invention pertains to certain fluorinatedcarboxylic acids and their carbonyl-derived derivatives, which containthree or more fully fluorinated carbon atoms and have two hydroxylgroups attached to the carbon atom adjacent to the carbonyl orderivative group.

The gem-diols of the invention when in acid form can be represented bythe formula in which R, is a perfiuoroalkyl group having from 3 to 20carbon atoms, from 3 to 12 carbon atoms being preferred.

These acids are water-soluble and useful for their acidic properties,being relatively strong acids. They can be used as a starting materialfor further reaction to produce other carbon-fluorine containingcompounds. They form salts with metals and ammonia as by neutralizationwith a base. Their alkali-metal salts are water-soluble and can be usedas emulsifying agents, particularly for use in systems where fluorinatedcompounds are present. Thus they can be used in wax emulsions, such asfloor wax and the like.

Further, by dehydration, acids having the formula wherein R, has thesame significance as before, are produced. These keto acids are usefulfor surfactants and emulsifiers, as in-non-aqueous polishing waxemulsions. The acids are also chemical intermediates, from which esters,amidine, nitriles, hydrazides and the like can be prepared by reactionwith the carboxyl group. When treated with water, the dihydroxy acid oracid derivative is reformed.

In preparing the compounds of the invention, a 1,2- epoxyperfiuoroalkane is employed as a starting material. The 1,2-epoxyperfiuoroalkane contains at least 3 carbon atoms, and preferably 5 ormore, with a distal CF group. Product compounds containing more thanabout 20 carbon atoms olfer no significant advantage in properties overthe shorter-chained acids, and the starting materials are difiicult toobtain and are more expensive than the preferred 1,2-epoxides containing3 to about 20 carbon atoms.

The selected starting epoxide is treated with water at temperatures ofthe order of to 200 C., and preferably to C., using closed vesselsequipped to withstand the pressure. A molar excess of water is used,e.g. from 2 to 5 moles of water per mole of starting epoxide. Thetreatment at the temperatures indicated is continued for a periodranging from 30 minutes up to 24 hours or more, the shorter times beingused with the higher temperatures and the longer times being used withthe lower temperatures.

The perfiuoroalkane epoxides employed as starting materials are obtainedby treating the corresponding perfluoroolefins (such as those disclosedin US. Pat. 2,668,- 864) with alkaline aqueous hydrogen peroxide. Theprocedure is as follows:

A mixture containing 3 moles of 35 percent aqueous hydrogen peroxide foreach mole of the selected 1,2-perfluoroalkene is stirred thoroughlywhile incrementally adding 1 mole of sodium carbonate for each mole ofthe perfluoroalkene, as a 10 percent aqueous solution. The reaction isexothermic and cooling means, agitation, and a suitable condenser areprovided. The rate of addition of the alkali is adjusted for control ofthe reaction. The temperature of the aqueous layer is maintained belowabout 60 C., preferably below about 50 C. After all of the alkali isadded, the fluorocarbon layer is separated and dried, e.g. overphosphorus pentoxide, and filtered. Any unreacted perfluoroalkene isremoved by slowly adding bromine to the solution at room temperature,while irradiating with ultraviolet light, until the color of brominepersists. The mixture is then fractionally distilled to separate thefiuoroalkyl epoxide from the fiuoroalkyl dibromide.

The following examples will more specifically illustrate the compoundsof the invention and the process for their production. All parts are byweight unless otherwise specified.

EXAMPLE 1 A glass ampoule is charged with 2.5 parts of 1,2-epoxyperfluoroheptane and 0.3 part of water. The ampoule is sealed, placed ina shaking autoclave and heated at 150 C. for about 20 hours. The ampouleis then cooled, opened and the white solid contained therein is removed,washed with water and dried. 2.2 parts of the white, solid product,consisting of alpha,alpha-dihydroxy perfluoroheptanoic acid, areobtained. The acid softens at about 50 C. with formation of bubbles,indicating dehydration is taking place. Decomposition of the dehydratedproduct, the alpha-keto perfluoroheptanoic acid, take place in the rangeof 80 to 115 C.

The sodium salt of the dihydroxy perfluoroheptanoic acid thus formed isobtained by neutralizing an aqueous solution of the acid to pH 7 with 1N sodium carbonate solution. Evaporation of the solution in a vacuumoven at about 50 C. yields the sodium salt as a white powder.

To dehydrate the dihydroxy acid, a portion of the acid obtained above isplaced in a glass container provided with a heating mantle and vacuumconnection. While maintaining the vessel at approximately 1 mm. Hgpressure, the acid is gentlyheated at about 60 C. A white solid remains,consisting of alpha-keto perfluoroheptanoic acid.

EXAMPLE 2 A glass ampoule is charged with 50 parts of 1,2-epoxyperfiuorodecaneand 5.5 parts of water. The ampoule is sealed, placed ina rocking autoclave and heated at 140 to 155 9 C. for about 20 hours.

After cooling and opening the ampoule, the gaseous products formed inthe reaction are removed by connecting the ampoule to a vacuum systemand gently warming. The remaining substantially white solid isalpha,alpha-dihydroxy perfluorodecanoic acid.

The acid is dissolved in water, neutralized to pH 7 with 1 N sodiumcarbonate solution and the waterv isremoved by evaporation in vacuum.oven at .40 50f C. The sodium salt is obtained as a white powder.

The alpha,alpha-dihydroxy perfiuorodecanoic acid is dehydrated to formalpha-keto perfiuorodecanoic acid by the procedure set forth in Example1.

In a similar way, starting with 1,2-epoxy perfiuorododecane, 1,2-epoxyperfiuorooctane and 1,2-epoxy perfluoropentane, using 3 moles of waterfor each mole of starting material, and heating as set forth above,there are obtained respectively, alpha,alpha-dihydroxyperfiuorododecanoic acid, alpha,alpha-dihydroxy perfiuorooctanoic acidand alpha,alpha-dihydroxy perfluoropentanoic acid. These, ondehydration, yield alpha-keto perfluorododecanoic acid, alpha-ketoperfiuorooctanoic acid and alpha-keto perfluoropentanoic acid,respectively.

The alpha,alpha-dihydroxy fluoroalkyl acids have been found to undergomany of the reactions characteristic of the known perfluoroalkylcarboxlic acids, providing that care is taken to avoid conditions whichwill result in dehydration to the keto acid, in cases where water wouldinterfere with the reaction, and if dehydration conditions are used, tomaintain temperatures and reaction condition which will avoiddecomposition of the alpha-keto compound.

The acids and their derivatives can be characterized by the formula orhydroxy alkyl; and when Q is CH Z is OR',

' o R i oiio cnz NRR" and R H I -Nrroot l=cl;rz

where-R and R areas hereinbefore. For convenience, these derivatives,including 'the polymers formed by polymerizing the vinyl-groupcontainingderivatives, can be referred to generally as carbonyl-derivedderivatives.

The salts can be prepared by standard methods as exemplified, insolution or in solid form by evaporation of solvent at temperaturesbelow about 60 C., if necessary under reduced pressure.

The methylester can be readily prepared by, for example, theconventional diazomethane reaction, preferably in ether solution atabout room temperature. The other esters are suitably prepared byconventional ester exchange reactions using, for example, no solvent oran inert solvent such as diethyl ether or diglyme with atetrabutyltitanate catalyst. Excess ester reactants and product acid canbe removed by, for example, distillation at reduced pressure or byextraction with a cold hydrocarbon such as heptaine, in which thedihydroxy ester is substantially insoluble but which has high solubilityfor the hydrocarbon compounds.

Amides, substituted or unsubstituted, can generally be prepared byreaction of the methyl ester in ether solution or without solvent byreaction at room temperature or below with ammonia or a substitutedamine. Ammonia and the aliphatic primary and secondary amines arepreferred since the aromatic amines tend to act only slowly.

1,1-dihydroamines,

can be prepared by reduction of the corresponding amide Rl |5CNRR withRaney nickel and hydrogen in ether solution at temperatures of to 40 C.

The acids can be converted to trihydric alcohol,

| H RIC-C OH I H 0 H by reduction of the acid with sodium borohydride indiglyme or tetrahydrofuran solution at temperatures of about to C. Theprimary hydroxyl group is considerably more reactive than the secondarygem hydroxyl group. In transesterification, for example, the primarygroup reacts almost exclusively. Treatment of the alcohol with, forexample, methyl acrylate or methyl methacrylate in presence oftetrabutyltitanate produces the dihydroxy acrylate or methacrylateester,

The alpha,alpha-dihydroxy acid salts are valuable surfactants. Where R;contains 3 or more carbon atoms, the materials will depress the surfacetension of aqueous solutions and particularly in the case of the longerchain compounds, are sufficiently more water-soluble than thefluoroalkyl carboxylic acid derivatives to be preferable in such uses asleveling agents for latex paints, aqueousbased wax polish emulsions andthe like.

The polymers and the copolymers prepared from the vinyl esters or theacrylates or methacrylates of l,l-dihydro-2,2-dihydroxy fiuoro-alcoholsresemble in physical characteristics the corresponding polymers of theknown fiuoroalkyl acids and esters. The polymers are oil repellent andwater repellent; however, the gem dihydroxy groups provide polar centersin the polymer which allows the polymer to be somewhat plasticized bylow molecular weight polar molecules such as water, acetone, methanoland the like, thus providing softer polymers which are still not solublein the presence of the plasticizing liquids. As surface treatments forfabrics, the acrylates and methacrylates produce a finish which has thedesirable stain re- 5 sistance of the previously known fiuoroalkylderivatives, References Cited but which generally has a softer and morepleasant hand. UNITED STATES PATENTS What is claimed is: L A compound ofthe formula 3,321,517 5/ 1967 Selman 260-535X OH FOREIGN PATENTS1,485,419 5/1967 France 260--535 6 LORRAINE A. WEINBERGER, PrimaryExaminer 0 P. J. KILLOS, Assistant Examiner wherein R is aperfluoroalkyl radical having from 3 to 2 10 carbon atoms.

2- Alpha,alpha-dihydoxy perfluoroheptanoic acid- 204163; 252-86, 356;260-348, 348.5, 408, 465.7,

T e sodium salt of p p v yp 476, 479, 483, 484, 486, 539, 561, 562, 564,569, 571, 573, heptanic acid. 574, 576

